Stranglehold

Enchantment

Your opponents can't search libraries.
If an opponent would begin an extra turn, that player skips that turn instead.

2011-09-22:
An “extra turn” means a turn created by a spell or ability. It doesn’t refer to a turn taken in a sanctioned tournament after the time limit for the round has expired.
2011-09-22:
If an opponent’s extra turn is created while Stranglehold is on the battlefield, but Stranglehold leaves the battlefield before that turn would begin, that opponent takes the extra turn as normal.
2011-09-22:
If an effect says “You may search your library . . . If you do, shuffle your library” or “You may search your library . . . then shuffle your library,” your opponents can’t choose to search, so they won’t shuffle.
2011-09-22:
If an effect says “Search your library . . . then shuffle your library,” your opponents shuffle their libraries even though they can’t search.
2011-09-22:
Effects that instruct your opponents to reveal or look at cards from the top of their libraries will still work. Only effects that use the word “search” are affected.